Electron-emitting device and manufacturing method thereof

ABSTRACT

There is provided an electron-emitting device of a field emission type, with which the spot size of an electron beam is small, an electron emission area is large, highly efficient electron emission is possible with a low voltage, and a manufacturing process is easy. The electron-emitting device includes a layer  2  which is electrically connected to a cathode electrode  5,  and a plurality of particles  3  which contains a material having resistivity lower than that of a material constituting the layer  2,  and is wherein a density of particles  3  in the layer  2  is 1×10 14 /cm 3  or more and 5×10 18 /cm 3  or less.

TECHNICAL FIELD

The present invention relates to an electron-emitting device using anelectron-emitting film, an electron source having a plurality ofelectron-emitting devices arranged therein, and an image displayapparatus constituted by using the electron source.

BACKGROUND ART

In the case of applying an electron-emitting device using anelectron-emitting film to an image display apparatus using phosphors,the electron-emitting device is demanded to realize an emission currentsufficient for causing the phosphors with sufficient luminance. Inaddition, the size of an electron beam to be irradiated on the phosphorsis demanded to be smaller for higher resolution (definition) of theimage display apparatus (display). Moreover, it is important that theapparatus itself is easily manufactured.

A cold cathode electron source, which is one type of theelectron-emitting device, includes a field emission type (hereinafterreferred to as “FE type”), a surface conduction electron-emittingdevice, or the like.

For the FE type, a Spindt type is highly efficient and expected.However, an electron-emitting device of the Spindt type has acomplicated manufacturing process and, moreover, tends to disperse anelectron beam. Thus, it is necessary to arrange a focusing electrodeabove an electron-emitting part in order to prevent spreading of theelectron beam.

On the other hand, as examples of an electron-emitting device with whichthe spot size of an electron beam does not increase so much as that withthe Spindt type, there are those disclosed in, for example, JP 08-096703A, JP 8-096704 A, JP 8-264109 A, and the like. Those electron-emittingdevices cause electrons to be emitted from a flat thin film(electron-emitting film) arranged in a hole thereof. Thus, a relativelyflat equipotential surface is formed on the electron-emitting film andwidening of an electron beam is reduced, while the electron-emittingdevices can be manufactured relatively easily. In addition, reduction ofa drive voltage necessary for electron emission can be realized by usinga material of a low work function as a substance forming theelectron-emitting film. Moreover, the electron emission is performed ina planar shape (in the Spindt type, it is performed in a dot shape), sothat concentration of electric fields can be relaxed. Thus, long life ofthe electron-emitting device can be realized. A carbon basedelectron-emitting film has been proposed as such a flatelectron-emitting film. An electron-emitting device using a carbon basedfilm is disclosed in, for example, “A study of electron field emissionas a function of film thickness from amorphous carbon films” R. D.Forrest et al., Applied Physics Letters, Volume 73, Number 25, 1988, P3784; or the like. Further, examples of carbon films having variousmetals added therein are disclosed in, for example, “Electron fieldemission from Ti-containing tetrahedral amorphous carbon films depositedby filtered cathodic vacuum arc” X. Z. Ding et al. Journal of appliedphysics Volume 88, Number 11, 2000, P 6842; “Field emission fromcobalt-containing amorphous carbon composite films heat-treated in anacetylene ambient” Y. J. Li et al. Applied Physics Letters, Volume 77,Number 13, 2000, p 2021; “Low-macroscopic-field electron emission fromcarbon films and other electrically nanostructured heterogeneousmaterials: hypotheses about emission mechanism” Richard G. Forbes,Solid-State Electronics 45(2001) pp. 779-808; “Field emission frommetal-containing amorphous carbon composite films” S. P. Lau et al.,Diamond Related Materials, 10(2001) pp. 1727-1731; JP 2001-006523 A; JP2001-202870 A; and the like.

In addition, electron-emitting films using a conductive material and aninsulating material are studied in various ways. Such electron-emittingfilms are disclosed in, for example, “Enhanced cold-cathode emissionusing composite resin-carbon coatings” S. Bajic and R. v. Latham., J.Phys. D: Appl. Phys. 21(1988) pp. 200-204; “Field emitting inks forconsumer-priced broad-area flat-panel displays” A. P. Burden et al., J.Vac. Sci. Technol. B 18(2), March/April (2000) pp. 900-904; JapaneseUtility Model Application Laid-open No. 04-131846; and the like.Moreover, there are reports on electron-emitting films such as one inwhich a conductive material is added in pores of an insulating materialas disclosed in JP 2001-101966 or one in which, in a cermet of ceramicsand metal, electrons are injected into an insulating layer from themetal to emit the electrons as disclosed in U.S. Pat. No. 4,663,559.

DISCLOSURE OF INVENTION

FIG. 18 shows an example in which an electron-emitting device is appliedas an image display apparatus 1000. Lines of a gate electrode layer 1002and lines of a cathode electrode layer 1004 are arranged on a substrate1001 in a matrix shape, and electron-emitting devices 1014 are arrangedin crossing parts of both the lines. Electrons are emitted from theelectron-emitting device 1014 placed in a selected crossing partaccording to an information signal, and accelerated by a voltage of ananode 1012 to be incident to the phosphors 1013. Such a device is aso-called triode device. Note that reference numeral 1003 denotes aninsulating layer.

In the case in which the application to the image display apparatus isconsidered with a field emission electron-emitting device, it isdemanded that the following requirements are satisfied simultaneously:

-   (1) a spot size of an electron beam (electron beam diameter) is    small;-   (2) an electron-emitting area is large;-   (3) an electron emission site density (ESD) is high and a current    density is high;-   (4) highly efficient electron emission is possible with a low    voltage; and-   (5) a manufacturing process is easy.

However, the above-mentioned conventional device using anelectron-emitting film cannot always be realized in a state in which theabove-mentioned requirements can be satisfied simultaneously.

Therefore, the present invention has been devised in order to solve theabove-mentioned problems of the conventional art, and it is an object ofthe present invention to provide: a field emission electron-emittingdevice with which the spot size of an electron beam (electron beamdiameter) is small, an electron-emitting area is large, highly efficientelectron emission is possible with a low voltage, and a manufacturingprocess is easy; an electron source; and an image display apparatus.

A constitution of the present invention devised for attaining theabove-mentioned object is as described below.

That is, according to the present invention, there is provided anelectron-emitting device including: a cathode electrode; a layerelectrically connected to the cathode electrode; and a plurality ofparticles comprising as a main component a material which hasresistivity lower than resistivity of a material of the layer, whereinthe plurality of particles are arranged in the layer; and a density ofthe particles in the layer is 1×10¹⁴/cm³ or more and 5×10¹⁸/cm³ or less.

Further, according to the present invention, there is provided anelectron-emitting device including: a cathode electrode; a layerelectrically connected to the cathode electrode; and a plurality ofparticles comprising a material, which has resistivity lower thanresistivity of a material of the layer, as a main component, wherein theplurality of particles are arranged in the layer; and a concentration ofa main element of the particles with respect to a main element of thelayer is 0.001 atm % or more and 1.5 atm % or less.

Further, according to the present invention, there is provided anelectron-emitting device including: a cathode electrode; a layerelectrically connected to the cathode electrode; and a plurality ofparticles comprising as a main component a material which hasresistivity lower than resistivity of a material of the layer, whereinthe plurality of particles are arranged in the layer; a density of theparticles in the layer is 1×10¹⁴/cm³ or more and 5×10¹⁸/cm³ or less; anda concentration of a main element of the particles with respect to amain element of the layer is 0.001 atm % or more and 1.5 atm % or less.

Further, according to the present invention, there is provided anelectron-emitting device including: a cathode electrode; a layer whichis arranged on the cathode layer and contains carbon as a maincomponent; and at least two particles which are arranged so as to beadjacent to each other in the layer and each comprises metal as a maincomponent, wherein one of the adjacent two particles is arranged to benearer to the cathode electrode than the other particle; and the metalis metal selected from Co, Ni, and Fe.

Further, according to the present invention, there is provided anelectron-emitting device including: a cathode electrode; and a layerconnected to the cathode electrode, wherein a plurality of groups ofparticles, each group being constituted by at least two particlesadjacent to each other, are arranged in the layer; the particlescomprises as a main component a material which has resistivity lowerthan resistivity of a material of the layer, the adjacent two particlesare arranged in a range of 5 nm or less; one of the adjacent twoparticles is arranged to be nearer to the cathode electrode than theother particle; and the plurality of groups of particles are arrangedapart from each other by an average film thickness of the layer or more.

Further, according to the present invention, there is provided anelectron-emitting device including: a cathode electrode; and a layerconnected to the cathode electrode, wherein a plurality of groups ofparticles, each group being constituted by at least two particles whichcomprises metal as a main component and are adjacent to each other, arearranged in the layer; the layer comprises as a main component amaterial which has resistivity higher than resistivity of the particlescomprising metal as a main component; the adjacent two particles arearranged in a range of 5 nm or less; and one of the adjacent twoparticles is arranged to be nearer to the cathode electrode than theother particle.

Further, according to the present invention, there is provided anelectron-emitting device including: a cathode electrode; and a layerwhich is connected to the cathode electrode and comprises carbon as amain component, wherein a plurality of groups of particles, each groupbeing constituted by at least two particles which comprises metal as amain component and are adjacent to each other, are arranged in thelayer; the plurality of groups of particles are arranged apart from eachother by an average film thickness of the layer or more; and aconcentration of the metal in the carbon layer is lower on a surfaceside of the carbon layer than on the cathode electrode side.

Further, according to the present invention, there is provided anelectron-emitting device including: a cathode electrode; and a layerwhich is connected to the cathode electrode and comprises carbon as amain component, wherein a plurality of groups of particles, each groupbeing constituted by two particles which comprises metal as a maincomponent and are adjacent to each other, are arranged in the layer, oneof the adjacent two particles is arranged to be nearer to the cathodeelectrode than the other particle; and graphen is included betweenadjacent particles in at least part of the plurality of particles.

Further, according to the present invention, there is provided anelectron-emitting device including: a cathode electrode; a layer whichis electrically connected to the cathode electrode and comprises carbonas a main component; and a plurality of conductive particles arranged inthe layer comprising carbon as a main component, wherein the layercomprising carbon as a main component contains a hydrogen element of 0.1atm % or more with respect to a carbon element.

According to the electron-emitting device of the present invention, itis preferable that the layer comprising carbon as a main componentcontains a hydrogen element of 1 atm % or more and 20 atm % or less withrespect to a carbon element.

Further, it is preferable that surface unevenness of the layer issmaller than 1/10 of its film thickness in rms.

Further, it is preferable that the layer contains carbon as a maincomponent.

Further, it is preferable that an average concentration of hydrogen withrespect to carbon in the layer is 0.1 atm % or more.

Further, it is preferable that the layer comprising carbon as a maincomponent has an sp³ bonding.

Further, it is preferable that the particles contain metal as a maincomponent.

Further, it is preferable that the metal is metal selected from Co, Ni,and Fe.

Further, it is preferable that the particles comprise monocrystal metalas a main component.

Further, it is preferable that the particles have an average particlediameter of 1 nm or more to 10 nm or less.

Further, it is preferable that the layer has a thickness of 100 nm orless.

Further, it is preferable that at least two adjacent particles among theplurality of particles are arranged 5 nm or less apart from each other.

Further, it is preferable that a density of the particles in the layeris 1×10¹⁴/cm³ or more and 5×10¹⁸/cm³ or less, in particular, 1×10¹⁵/cm³or more and 5×10¹⁷/cm³ or less.

Further, it is preferable that a concentration of a main element of theparticles with respect to a main element of the layer is 0.001 atm % ormore and 1.5 atm % or less, in particular, 0.05 atm % or more and 1 atm% or less.

Further, it is preferable that: a plurality of particles are arrangeddispersedly in the layer as a plurality of groups of particles, eachgroup being constituted by at least two adjacent particles; one of thetwo adjacent particles are placed to be nearer to the cathode electrodethan the other particle; and the plurality of groups of particles arearranged apart from each other by an average film thickness of the layeror more.

Further, the electron-emitting device of the present invention furtherincludes: an insulating film which is arranged on the cathode electrodeand has a first opening; and a gate electrode which is arranged on theinsulting film and has a second opening, and it is preferable that: thefirst opening and the second opening communicate with each other; andthe layer is exposed in the first opening.

Further, according to the present invention, there is provided anelectron source, wherein a plurality of the electron-emitting devices ofthe present invention are arranged.

Further, according to the present invention, there is provided an imagedisplay apparatus, characterized by including: the electron source ofthe present invention; and a light-emitting member which emits light bybeing irradiated with electrons.

Further, according to the present invention, there is provided amanufacturing method for an electron-emitting device, characterized byincluding: forming a layer which comprises metal and a material havingresistivity higher than that of the metal as a main component; andheating the layer in an atmosphere containing hydrogen.

According to the manufacturing method of the present invention, it ispreferable that the atmosphere containing hydrogen further containshydrocarbon.

Further, it is preferable that the hydrocarbon is acetylene.

Further, it is preferable that the metal is a VIII group element.

Further, it is preferable that the metal is selected from Co, Ni, andFe.

Further, it is preferable that a heat treatment temperature in theheating is 450° C. or more.

Further, it is preferable that the layer comprising a material havingresistivity higher than that of the metal as a main component is a layercontaining carbon as a main component.

Further, it is preferable that the metal is contained in the layercomprising carbon as a main component before the heating at a ratio of0.001 atm % or more and 5 atm % or less, in particular, 0.001 atm % ormore and 1.5 atm % or less, with respect to the carbon element.

Further, it is preferable that the film comprising carbon as a maincomponent before the heating has an sp³ bonding.

According to the present invention described above, electron emissionwith a high density and stable of a current to be emitted in a lowelectric field can be obtained and, at the same time, an electron beamof high resolution can be realized. Moreover, an electron-emittingdevice exhibiting the above effects can be realized easily. Thus, in anelectron source and an image display apparatus to which theelectron-emitting device of the present invention is applied, a highperformance electron source and image display apparatus can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view showing a structure of anelectron-emitting device in accordance with the present invention;

FIG. 2 is an explanatory graph of an embodiment mode in accordance withthe present invention;

FIGS. 3A and 3B are explanatory graphs of the embodiment mode inaccordance with the present invention;

FIGS. 4A, 4B, 4C, and 4D are schematic views showing an example of amanufacturing method of the electron-emitting device in accordance withthe present invention;

FIG. 5 is a structural diagram showing an electron source of a passivematrix arrangement in accordance with the present invention;

FIG. 6 is a schematic structural diagram showing an image displayapparatus using the electron source of a passive matrix arrangement inaccordance with the present invention;

FIG. 7 is a drive circuit diagram of the image display apparatus usingthe electron source of a passive matrix arrangement in accordance withthe present invention;

FIGS. 8A(a), 8A(b), and 8A(c) are schematic views showing anelectron-emitting device in accordance with a first embodiment of thepresent invention;

FIGS. 8B(a), 8B(b), and 8B(c) are schematic views showing anelectron-emitting device in accordance with a second embodiment of thepresent invention;

FIG. 9 is a graph showing a volt-ampere characteristic of theelectron-emitting device in accordance with the present invention;

FIGS. 10A, 10B, and 10C are schematic views showing an electron-emittingdevice in accordance with a third embodiment of the present invention;

FIG. 11 is an apparatus diagram in accordance with a third embodiment ofthe present invention;

FIG. 12 is a graph showing a volt-ampere characteristic of theelectron-emitting device in accordance with the present invention;

FIGS. 13A, 13B, and 13C are schematic views showing an electron-emittingdevice in accordance with a fourth embodiment of the present invention;

FIGS. 14A, 14B, and 14C are schematic views showing an electron-emittingdevice in accordance with a fifth embodiment of the present invention;

FIG. 15 is a schematic view showing an electron-emitting device inaccordance with a sixth embodiment of the present invention;

FIGS. 16A and 16B are a schematic sectional view and a schematic planview, respectively, showing the electron-emitting device in accordancewith the present invention;

FIG. 17 is a graph showing a volt-ampere characteristic of theelectron-emitting device in accordance with the present invention;

FIG. 18 is a view schematically showing an example of an image displayapparatus employing a triode structure using a conventionalelectron-emitting device;

FIGS. 19A, 19B, and 19C are schematic sectional views showing an exampleof a manufacturing method in accordance with the present invention;

FIG. 20 is a schematic sectional view showing an example of theelectron-emitting device in accordance with the present invention;

FIG. 21 is a schematic sectional view showing an example of theelectron-emitting device in accordance with the present invention;

FIG. 22 is a schematic plan view showing an example of theelectron-emitting device in accordance with the present invention;

FIGS. 23A, 23B, 23C, and 23D are schematic sectional views showing anexample of the manufacturing method in accordance with the presentinvention;

FIGS. 24A, 24B, 24C, and 24D are schematic sectional views showing anexample of the manufacturing method in accordance with the presentinvention; and

FIG. 25 is a schematic plan view showing an example of theelectron-emitting device in accordance with the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiment modes of the present invention will be hereinafterdescribed illustratively in detail with reference to the accompanyingdrawings. Note that dimensions, materials, shapes and relativearrangements of components described in the following embodiment modesare not meant to limit a scope of the present invention solely theretounless specifically described otherwise.

FIG. 1 shows a schematic partial sectional view of an example of anelectron-emitting device of the present invention. In FIG. 1, referencenumeral 1 denotes a substrate; 2, a layer containing a plurality ofparticles 3; 3, particles; and 5, a cathode electrode. It is preferableto arrange a resistance layer between the cathode electrode 5 and thelayer 2 as required.

In an electron-emitting apparatus (including an image display apparatus)using the electron-emitting device of the present invention, forexample, as shown in FIGS. 16A and 16B, a triode structure is generallyadopted. In the triode structure, usually, an anode electrode 12 isarranged so as to be substantially parallel with the surface of thesubstrate 1, on which the electron-emitting device (the cathodeelectrode 5 and the layer 2) is arranged, and a gate electrode (electronextracting electrode) 8 is further arranged between the anode electrode12 and the layer 2 constituting the electron-emitting device, therebydriving the device. Upon driving, a potential, which is higher than thatapplied to the cathode electrode 5, is applied to the gate electrode 8,whereby electrons are emitted from the layer 2 in a substantiallyvertical direction with respect to the surface of the substrate 1. Notethat, although the example of the electron-emitting device of the triodestructure is described here, it is also possible to remove the gateelectrode 8 (and insulating layer 7) in FIGS. 16A and 16B and use theanode electrode 12 as an electron extracting electrode by giving apotential for drawing electrons from the layer 2. Such a structure is aso-called “diode structure”.

Resistivity of a main component of the layer 2 containing the pluralityof particles 3 is set higher than resistivity of the particles 3. Thus,basically, the main body of the layer 2 is constituted by a dielectricbody and a main body of the particles 3 is constituted by a conductor.By setting the resistivity of the main body of the layer 2 to 100 timesor more of that of the main body of the particles 3, electron emissioncan be performed in a lower electric field.

In addition, as a material to be the main body of the layer 2 containingthe plurality of particles 3, a material having smaller dielectricconstant is more preferable when only electric field concentration,which is described later in detail, is taken into account. However, whenit is taken as an electron-emitting material, preferably, carbon isused. In addition, in the case in which carbon is used, it is preferablethat the layer 2 has both sp² bonding and an sp³ bonding therein. Inparticular, a carbon film having a micro-structure of graphite (graphen)and a band structure containing the sp³ bonding is originally low inelectric field concentration and favorable in an electron-emittingcharacteristic. Thus, the above-mentioned carbon film is used as themain body of the layer 2 and, moreover, the particles 3 are arranged inthe layer 2 in a structure to be described later, whereby a furthereffect of electric field concentration can be additionally achieved and,in particular, a preferable electron-emitting characteristic can berealized. However, as described above, it is important that the layer 2has high resistance while substantially functioning as an insulatingbody. Thus, it is preferable that a main body of the carbon film is anamorphous carbon such as diamond-like-carbon (DLC) because resistivityin the order of 1×10 to 1×10¹⁴ Ω cm can be obtained, and the carbon filmcan function as a dielectric body.

On the other hand, the particles 3 preferably contain metal as a mainbody thereof and, more specifically, contain a VIII group element.Moreover, in the case in which the main body of the layer 2 is carbon,the particles 3 is preferably metal selected from among Ni, Fe, and Coand, in particular, Co is preferable. Since there is less band barrierbetween Ni, Fe, or Co and carbon, obstacle in electron injection isless. In addition, the particles 3 preferably have a monocrystal (singlecrystal) of the metal as the main body in realizing a larger emissioncurrent density. In addition, stable electron emission becomes possiblein a further lower electric field and the electron-emittingcharacteristic becomes more preferable as graphen, which is themicrostructure of graphite, is arranged around the particles 3 (inparticular, between adjacent particles). Further, it is preferable touse Ni, Fe, or Co as the main body of the particles and use carbon asthe main body of the layer 2 because, in the case in which theelectron-emitting device of the present invention is produced through“cohesion (agglomeration)” to be described later, since graphitizationof carbon, which is the element constituting the layer 2, is easilygrown by heat treatment at a low temperature, a conduction path and themicrostructure of graphite can be formed easily.

In the present invention, the plurality of particles 3 is not alwaysdispersed uniformly in the layer 2. As schematically shown in FIG. 1,the plurality of particles 3 form aggregates (groups of particles) 10 tosome extent and, the aggregates (groups of particles) 10 are arrangeddiscretely in the layer 2. A distance among the respective aggregates(groups of particles) 10 is preferably equal to or more than an averagefilm thickness of the layer 2. Note that the average film thickness ofthe layer 2 is defined with the surface of the cathode electrode 5 (orthe surface of the substrate 1) as a reference. More specifically, thedistance among the respective aggregates (groups of particles) 10 isequal to or more than the average film thickness of the layer 2 and,preferably, 1.5 time or more to 1000 times or less thereof. In a rangeexceeding this, it becomes difficult for the electron emission sitedensity (ESD) in the layer 2 to satisfy a characteristic of theelectron-emitting device required of an image display apparatus.

In this way, the respective aggregates (groups of particles) 10 aresufficiently apart from each other, whereby a threshold value forelectron emission can be reduced. This is because, as the aggregates(groups of particles) 10 are apart from each other, there is an effectof increasing electric field concentration to the respective aggregates(groups of particles) 10. Note that, in the present invention, theparticles 3, which do not form the aggregates 10, may exist among therespective aggregates (groups of particles) 10.

Further, the plurality of particles constituting the respectiveaggregates (groups of particles) 10 are arranged so as to besubstantially aligned in a film thickness direction of the layer 2(direction toward the surface side of the layer 2 from the cathodeelectrode 5 side). According to such a structure, electric field can beconcentrated in the respective aggregates 10.

In the present invention, the number of particles 3 aligned in the filmthickness direction of the layer 2 is not limited and only has to be atleast two or more. For example, it is sufficient that two particles arealigned in the film thickness direction of the layer 2 with one of theadjacent two particles arranged in a position closer to the surface ofthe cathode electrode 5 (or the surface of the layer 2) than the other.However, in further reducing the threshold value for electron emission,it is preferable that the other particle is arranged in a positioncloser to the surface of the cathode electrode 5 (or the surface of thelayer 2) than a central position of the one particle and, moreover, theother particle is arranged in an area between the one particle and thesurface of the cathode electrode 5 (or the surface of the layer 2). Inthe present invention, the particles 3 are preferably aligned verticallywith respect to the surface of the cathode electrode 5 (surface of thelayer 2) but are not necessarily limited to such an arrangement.

In addition, in the present invention, the adjacent particles arepreferably arranged within a range of 5 nm or less. When this range isexceeded, the threshold value for electron emission starts to increaseextremely and it also becomes difficult to obtain a sufficient emissioncurrent. Further, in the respective aggregates (groups of particles),the adjacent particles 3 may be in contact with each other. It is notdesirable that the distance among the particles 3 exceeds the averageparticle diameter thereof because the electric field concentration isless likely to occur. In addition, as in the present invention, sincethe conductor contained in the layer 2 is a particulate, even if theadjacent particles are in contact with each other, resistance betweenthe adjacent particles increases. Thus, it is surmised that extremeincrease in an emission current at individual electron emission siteexisting in the layer 2 can be suppressed, and electron emission can beperformed stably.

Further, in the present invention, it is preferable that the particles 3are substantially embedded in the layer 2 completely but may bepartially exposed from the surface of the layer 2. Thus, unevenness ofthe surface of the layer 2 is preferably one tenth or less of theaverage film thickness of the layer 2 in “rms”. “rms” is defined asJapanese Industrial Standard. With this structure, dispersion of anelectron beam due to surface roughness of the layer 2 can be suppressedas much as possible. In addition, according to the above-mentionedstructure, since the surfaces of the particles 3 are less likely to beaffected by influence of gas existing in the vacuum, it is surmised thatthe structure contributes also to stable electron emission.

According to the electron-emitting device of the above-mentionedconstitution of the present invention, it is surmised that a conductionpath of the conductor particles 3 is formed partially (discretely).Thus, pre-processing such as conditioning, which has been conventionallyrequired of a carbon film with a flat surface, becomes unnecessary, andsatisfactory electron emission can be realized without suffering partialdestruction or damage. However, when the particles are disperseduniformly over solely the conduction path, that is, the entire layer 2,the threshold value for electron emission increases. In addition, whenthe distance among the respective aggregates (groups of particles) 10increases excessively, the electron emission current necessary for theelectron-emitting device used in the display and the electron emissionsite density necessary for stably flowing the electron emission currentcannot be obtained. As a result, stable electron emission and stabledisplay image cannot be obtained. For this reason, the density of theparticles 3 in the layer 2 is preferably 1×10¹⁴/cm³ or more and5×10¹⁸/cm³ or less. Moreover, if the density is 1×10¹⁵/cm³ or more and5×10¹⁷/cm³ or less, electron emission in a lower electric field can berealized. In addition, due to the same reason, a practical range of aconcentration of a main element constituting the particles 3 withrespect to a main element constituting the layer 2 is in a range of0.001 atm % or more and 1.5 atm % or less. Moreover, when theconcentration is 0.05 atm % or more and 1 atm % or less, electronemission in a lower electric field can be realized. When theconcentration exceeds the above-mentioned range, as described above, thethreshold value for electron emission increases. Further, a drivevoltage to be applied increases and, as a result, breakdown may becaused, or a sufficient electron emission site density cannot beobtained. Thus, an emission current density necessary for an imagedisplay apparatus cannot be secured.

Here, the above-mentioned range of numerical values will be described.The number of aggregates (groups of particles) 10 existing in the layer2 is shown in FIGS. 3A and 3B as a function of a density of particles.Note that X is the number of particles constituting one aggregate (agroup of particles).

When it is assumed that the density of the particles 3 in the layer 2 isP/cm³, the film thickness of the layer 2 is h, and the average radius ofthe particles is r, the number E of areas where the particles 3 continuein the film thickness direction (aggregates 10) is2rP(8r³P)^((h/2r-1))/cm². FIG. 3A is a graph at the time when r=2 nm andFIG. 3B is a graph at the time when r=5 nm. Note that, here, r indicatesa value of a half of the average particle diameter of the particles 3,and the average particle diameter of the particles 3 is preferably 1 nmor more and 10 nm or less as described later in detail.

It is desirable to set the density to a density with which electricfield concentration can occur in the groups of particles 10 and to set Eto be large. In order for two or more particles 3 to overlap forelectric field concentration and for the number E thereof to become1×10²/cm² or more and, preferably, 1×10⁴/cm² or more, it is sufficientthat P=1×10¹⁴/cm³ is satisfied in the case of r=2 nm. In addition, inorder for E to become 1×10⁴/cm or more, it is sufficient that at leastP=1×10¹⁴/cm³ is satisfied in the case of r=5 nm. On the other hand, whenP exceeds 5×10¹⁸/cm³, there are too many particles 3, and the layer 2becomes a mere conductor or electric field concentration to theaggregates 10 is less likely to occur. Thus, the ESD decreases and thecurrent density also decreases, which is not preferable for theelectron-emitting characteristic.

When the size of the particles 3 is controlled to several nm and thefilm thickness of the layer 2 is assumed to be several tens nm, it ispreferable that the range of P is 1×10¹⁴/cm³≦P≦5×10¹⁸/cm³, although thisdepends upon the film thickness of the layer 2 and the size of theparticles 3. In the case in which the average particle diameter (2r) ofthe particle 3 is 1 to 10 nm and the particles 3 contain Co as a mainbody, a Co concentration in the layer 2 satisfying the above-mentionedconditions is 0.001 to 1.5 atm %.

Ideally, the range of P is preferably 1×10¹⁵/cm³≦P≦5×10¹⁷/cm³. Forexample, in the example of FIGS. 3A and 3B, in the case in which therespective aggregates 10 are formed by two or more particlesoverlapping, the number E of the aggregates 10 is 1×10⁴/cm³ or more and1×10¹⁰/cm³ or less.

Here, electric field concentration will be described using FIG. 2. Whenit is assumed that a height of a conduction path is h, a radius of anelectron-emitting part is r, electric field concentration (2+h/r) aslarge occurs and, moreover, similar electric field concentration of anelectric field concentration factor β occurs due to a micro-shape of atip thereof, and electric field concentration of a multiplication ofthem (2+h/r)β occurs as a whole. Therefore, it is possible that, byadopting the above-mentioned form, an electron-emitting film with whichelectron emission is performed more easily can be constituted in theelectron-emitting device of the present invention.

On the other hand, a shape of a beam to be emitted is important informing a non-divergent beam in the case in which the film thickness ofthe layer 2 is as thin as 100 nm or less, although this depends upon thefilm thickness of the layer 2, the size and shape of the particles 3,and the design of an electric field or the like. Moreover, the layer 2has little structural stress and is suitable for a thin film process.When the size of the particles 3 is increased and the film thicknessincreases at the same ratio, the distance among the respective groups ofparticles 10 also increase and the number of electron emission sites perunit area decreases. The size of the particles 3 with respect to thesmall film thickness of 100 nm or less is ideally several nm (1 nm ormore and 10 nm or less), and the particles 3 preferably have a form inwhich several particles are arranged from the cathode electrode sidetoward the surface of the electron-emitting film.

Moreover, it is advisable to mix hydrogen in the layer 2 in order torelax a stress of the layer 2. For example, the layer 2 containingcarbon such as diamond-like-carbon (DLC) has high hardness and strongstress. Therefore, the layer 2 does not always have satisfactorycompatibility to a process including heat treatment. There is also aproblem in that, although it has a high quality as an electron-emittingfilm, it cannot be used as an electron-emitting device and an electronsource in the case in which it is unstable in terms of process. It isalso important that a film which is stable in process manufacturing canbe formed according to stress relaxation with hydrogen. Consequently, inthe case in which the main body of the layer 2 is carbon, stressrelaxation can be caused by containing a hydrogen element of 0.1 atm %or more with respect to a carbon element in the layer 2. In particular,when the hydrogen element of 1 atm % or more is contained, thisrelaxation is strong, and hardness and Young's modulus can be reduced.However, when the ratio of the hydrogen element with respect to thecarbon element exceeds 20 atm %, the electron-emitting characteristicstarts to deteriorate. Therefore, a substantial upper limit is 20 atm %.

Next, a manufacturing process of the electron-emitting device of thepresent invention will be described. However, it is needless to mentionthat this structure itself is an example and is not specificallylimited.

An example of a manufacturing method of the electron-emitting device inaccordance with an embodiment mode of the present invention will bedescribed with reference to FIGS. 4A to 4D. It is needless to mentionthat the present invention is not limited to this manufacturing method.In particular, an order of deposition and an etching method according toa difference of a structure are not limited, which will be describedseparately in an embodiment.

(Step 1)

First, in advance, one of: a laminated body formed by laminating SiO₂ onglass, soda lime glass, silicon substrate, or the like, a surface ofwhich is cleaned sufficiently and with content of impurity such asquartz glass, Na, or the like reduced, by a sputtering method or thelike; and an insulating substrate of ceramics such as aluminum is usedas the substrate 1 to laminate the cathode electrode 5 on the substrate1.

The cathode electrode 5 generally has electrical conductivity and isformed by a general vacuum deposition technique such as a vapordeposition method or a sputtering method. A material of the cathodeelectrode 5 is appropriately selected from, for example, a metal oralloy material such as Be, Mg, Ti, Zr, Hf, V, Nb, Ta, Mo, W, Al, Cu, Ni,Cr, Au, Pt, or Pd, a carbide such as Tic, ZrC, HfC, TaC, SiC, or WC, aboride such as HfB₂, ZrB₂, LaB₆, CeB₆, YB₄, or GdB₄, a nitride such asTiN, ZrN, or HfN, a semiconductor such as Si or Ge, amorphous carbon,graphite, diamond-like-carbon, carbon with diamond dispersed therein, acarbon compound, and the like. A thickness of the cathode electrode 5 isset in the range of several tens nm to several mm and, preferablyselected from the range of several hundreds nm to several μm.

(Step 2)

Subsequently, as shown in FIG. 4A, the layer 2 is deposited on thecathode electrode 5. The layer 2 is formed by a general vacuumdeposition technique such as an evaporation method, a sputtering method,or a Hot Filament CVD (HFCVD) method but is not limited to them. Athickness of the layer (electron-emitting film) 2 is set in the range ofseveral nm to hundred nm, and preferably selected from the range ofseveral nm to several tens nm. In addition, this step may be carries outafter step 6 to be described later (after forming an insulating layer 7having an opening and the gate electrode 8 having an opening) to depositthe layer 2 selectively on the cathode electrode 5 exposed in an opening9.

In the case of an rf sputtering method, for example, Ar is used as anatmosphere. However, for example, if Ar/H₂ is used, hydrogen can betaken into the layer 2. Parameters such as an rf power and a gaspressure may be decided appropriately.

Moreover, in the case in which cobalt is used as the main body of theparticles 3 and carbon is used as the main body of the layer 2, forexample, a method of using a multi-target which uses a graphite targetand a cobalt target, a method of controlling a cobalt content using onetarget in which graphite and cobalt are mixed, or the like can beselected appropriately.

(Step 3)

Then, a step of performing heat treatment to cause the material of theparticles 3 such as cobalt existing in the layer 2 to cohere (heattreatment to agglomerate the material of the particles) is performed,whereby the particles 3 is formed. However, the step of causing thematerial of the particles 3 to cohere may be performed later, and thematerial of the particles 3 is caused to cohere in a desired step. Theheat treatment is performed, for example, at 450° C. or more bylamp-heating. The heat treatment is performed in an atmospherecontaining hydrogen. However, it is preferable that the heat treatmentis performed in an atmosphere containing hydrogen and hydrocarbon gas interms of shortening the process. In addition, acetylene gas, ethylenegas, or the like is preferable as the hydrocarbon gas. In heat treatmentin mixed gas of hydrogen and acetylene gas, a cohering reaction of metal(Co) can be facilitated at an increasing speed while keeping planarityof the surface of the layer 2. In heat treatment in an N₂ atmosphere,unevenness of the surface of the layer 2 increases.

(Step 4)

Subsequently, the insulating layer 7 is deposited. The insulating layer7 is formed by the general vacuum deposition method such as thesputtering method, the CVD method, or the vacuum evaporation method, anda thickness thereof is set in the range of several nm to several μm, andpreferably selected from the range of several tens nm to severalhundreds nm. As a material for the insulating layer 7, a material withhigh withstanding pressure which can withstand a high electric fieldsuch as SiO₂, SiN, Al₂O₃, CaF, or undoped diamond is desirable.

(Step 5)

Moreover, the gate electrode 8 is deposited after the insulating layer 7is deposited (FIG. 4B). The gate electrode 8 has electrical conductivityin the same manner as the gate electrode 5 and is formed by the generalvacuum deposition technique such as the evaporation method or thesputtering method, or a photolithography technique. A material of thegate electrode 8 is appropriately selected from, for example, a metal oralloy material such as Be, Mg, Ti, Zr, Hf, V, Nb, Ta, Mo, W, Al, Cu, Ni,Cr, Au, Pt, or Pd, a carbide such as TiC, ZrC, HfC, TaC, SiC, or WC, aboride such as HfB₂, ZrB₂, LaB₆, CeB₆, YB₄, or GdB₄, a nitride such asTiN, ZrN, or HfN, or a semiconductor such as Si or Ge. A thickness ofthe gate electrode 8 is set in the range of several nm to several μm,and preferably selected from the range of several nm to several hundredsnm. Note that the electrodes 8 and 5 may be formed of an identicalmaterial or different materials and may be formed by an identicalforming method or different forming methods.

(Step 6)

Next, as shown in FIG. 4C, a mask M of an opening pattern is formed bythe photolithography technique and etching treatment is performed,whereby an electron-emitting device of a form shown in FIG. 4D can beformed. The gate electrode and the insulating layer 7 desirably have asmooth and vertical etching surface, and an etching method only has tobe selected according to materials of the gate electrode and theinsulating layer 7. The etching method may be dry or wet. Usually, adiameter W1 of the opening 9 is appropriately set according to amaterial forming a device or a resistance value of the device, a workfunction and a drive voltage of a material of an electron-emittingdevice, or a required shape of an electron emission beam. Usually, W1 isselected from the range of several hundreds nm to several tens μm.

Note that the electron-emitting device of the present invention is notlimited to the form shown in FIGS. 4A to 4D, 16A, and 16B in which theelectrode (gate electrode 8, etc.) for extracting electrons is arrangedabove the layer 2 arranged on the substrate. As shown in FIGS. 24D and25, the electron-emitting device of the present invention may be in aform in which the layer 2 serving as an electron-emitting layer and theelectrode (gate electrode 8) for extracting electrons from the layer 2are arranged on the surface of the substrate 1 so as to be opposed toeach other across a gap (space). FIG. 24D is a schematic sectional viewand FIG. 25 is a schematic plan view. Even in the case of theelectron-emitting device of the form shown in FIG. 24D, if an anodeelectrode is provided, a triode structure can be obtained by arrangingthe anode electrode above the substrate 1 as shown in FIG. 16A. Notethat, although the form in which the layer 2 remains on the gateelectrode 8 is illustrated in FIGS. 25 and 26, it is not alwaysnecessary that the layer 2 remain on the gate electrode 8.

In addition, preferably, in the electron-emitting device of the presentinvention, the surface of the layer 2 is terminated with hydrogen. Byterminating the surface of the layer 2 with hydrogen, emission ofelectrons can be further facilitated.

Next, an example of application of the electron-emitting device to whichthe present invention is applied will be hereinafter described. Aplurality of electron-emitting devices of the present invention arearranged on a substrate, whereby, for example, an electron source or animage display apparatus can be constituted.

Various arrangements of electron-emitting devices are adopted. As anexample, there is a passive matrix arrangement in which a plurality ofelectron-emitting devices are arranged in a matrix shape in an Xdirection and a Y direction, one of electrodes of the plurality ofelectron-emitting devices arranged on the same row is commonly connectedto wiring in the X direction and the other of electrodes of theplurality of electron-emitting devices arranged on the same column iscommonly connected to wiring in the Y direction.

The electron source of the passive matrix arrangement obtained byarranging the plurality of electron-emitting devices, to which thepresent invention is applicable, will be hereinafter described usingFIG. 5. In FIG. 5, reference numeral 91 denotes an electron sourcesubstrate; 92, X direction wirings; and 93, Y direction wirings.Reference numeral 94 denotes the electron-emitting device of the presentinvention.

The m X direction wirings 92 consist of Dx1, Dx2, . . . Dxm and can beconstituted by conductive metal or the like which is formed using thevacuum evaporation method, the print method, the sputtering method, orthe like. A material, a film thickness, and a width of the wirings areappropriately designed. The Y direction wirings 93 consist of n wiringsof Dy1, Dy2, . . . Dyn and are formed in the same manner as the Xdirection wirings 92. Not-shown interlayer insulating layers areprovided among the m X direction wirings 92 and the n Y directionwirings 93 and separate both the wirings electrically (both m and n arepositive integers).

The not-shown interlayer insulating layers are constituted by SiO₂ orthe like which is formed using the vacuum evaporation method, the printmethod, the sputtering method, or the like. For example, the interlayerinsulating layers are formed in a desired shape on the entire surface ora part of the surface of the substrate 91 on which the X directionwirings 92 are formed. In particular, a film thickness, a material, anda manufacturing method thereof are set such that the interlayerinsulating layer can withstand a potential difference at crossing partsof the X direction wirings 92 and the Y direction wirings 93. The Xdirection wirings 92 and the Y direction wirings 93 are drawn out asexternal terminals, respectively.

A pair of device electrodes (i.e., the above-mentioned electrodes 5 and8) constituting the electron-emitting device 94 are connectedelectrically by the m X direction wirings 92, the n Y direction wirings93, and connections consisting of conductive metal or the like.

A material constituting the X direction wirings 92 and the Y directionwirings 93, a material constituting the connection, and a materialconstituting the pair of device electrodes may be identical with eachother or may be different from each other in a part or all ofconstituent elements thereof. These materials are appropriatelyselected, for example, according to the material of the above-mentioneddevice electrodes (electrodes 5 and 8). In the case in which thematerial constituting the device electrodes and the wiring material areidentical, it can be said that the wirings connected to the deviceelectrodes are device electrodes.

Not-shown scanning signal application means, which applies a scanningsignal for selecting a row of the electron-emitting devices 94 arrangedin the X direction, is connected to the X direction wirings 92. On theother hand, not-shown modulation signal generation means for modulatingeach row of the electron-emitting devices 94 arranged in the Y directionaccording to an input signal is connected to the Y direction wirings 93.A drive voltage applied to each electron-emitting device is supplied asa differential voltage of the scanning signal and the modulation signalapplied to the device.

In the above-mentioned constitution, an individual device can beselected and driven independently using the passive matrix wirings. Animage display apparatus constituted by using an electron source of sucha passive matrix arrangement will be described using FIG. 6. FIG. 6 is aschematic view showing an example of a display panel of the imagedisplay apparatus.

In FIG. 6, reference numeral 91 denotes an electron source substrate onwhich a plurality of electron-emitting devices are arranged; 101, a rearplate on which the electron source substrate 91 is fixed; and 106, aface plate in which a fluorescent film 104 serving as a phosphor, ametal back 105, and the like, which are image forming members, areformed inside a glass substrate 103. Reference numeral 102 denotes asupport frame, and the rear plate 101 and the face plate 106 areconnected to the support frame 102 using frit glasses or the like.Reference numeral 107 denotes an envelope, which is sealed andconstituted by, for example, being baked for 10 minutes or more in thetemperature range of 400 to 500° C. in the atmosphere or in nitrogen.Reference numeral 94 corresponds to the electron-emitting device in thepresent invention. Reference numerals 92 and 93 denote X directionwirings and Y direction wirings connected to the pair of electrodes 8and 5 of the electron-emitting devices.

As described above, the envelope 107 is constituted by the face plate106, the support frame 102, and the rear plate 101. Since the rear plate101 is provided mainly for the purpose of increasing the strength of thesubstrate 91, the separately provided rear plate 101 can be madeunnecessary if the substrate 91 itself has the sufficient strength. Thatis, the support frame 102 may be directly sealed to the substrate 91 toconstitute the envelope 107 with the face plate 106, the support frame102, and the substrate 91. On the other hand, the envelope 107 havingthe sufficient strength against the atmospheric pressure can also beconstituted by setting a not-shown support body called a spacer betweenthe face plate 106 and the rear plate 101.

Note that, in the image display apparatus using the electron-emittingdevice of the present invention, phosphors (fluorescent film 104) arearranged above the electron-emitting device 94 in alignment taking intoaccount a trajectory of emitted electrons. In the present invention,since an electron beam reaches immediately above the electron-emittingdevice 94, the image display apparatus is constituted by positioning thefluorescent film 104 so as to be arranged immediately above theelectron-emitting device 94.

Next, a vacuum sealing process for sealing an envelope (panel) subjectedto the sealing process will be described.

The vacuum sealing process exhausts the envelope (panel) 107 through anexhaust pipe (not shown) with an exhaust apparatus such as an ion pumpor an absorption pump to obtain an atmosphere with sufficiently littleorganic substance while heating the envelope (panel) 107 and keeping itat 80 to 250° C. and, then, heats the exhaust pipe with a burner to meltand seal it completely. In order to maintain a pressure after sealing ofthe envelope 107, getter processing can also be performed. This isprocessing for heating a getter, which is arranged in a predeterminedposition (not shown) in the envelope 107, with heating using resistanceheating, high frequency heating, or the like to form an evaporation filmimmediately before performing the sealing of the envelope 107 or afterthe sealing. The getter usually contains Ba or the like as a maincomponent thereof and maintains an atmosphere in the envelope 107according to an absorption action of the evaporation film.

In the image display apparatus constituted by using the electron sourceof the passive matrix arrangement manufactured by the above-mentionedprocess, electron emission is caused by applying a voltage to therespective electron-emitting devices via terminals outside the case Dox1to Doxm and Doy1 to Doyn. In addition, a high voltage Va is applied tothe metal back 105 or a transparent electrode (not shown) via a highvoltage terminal 113 to accelerate an electron beam. Acceleratedelectrons collide against the fluorescent film 104 and emits light,whereby an image is formed.

Next, an example of a structure of a drive circuit for performingtelevision display, which is based upon a television signal of the NTSCsystem, on the display panel constituted by using the electron source ofthe passive matrix arrangement will be described using FIG. 7. In FIG.7, reference numeral 121 denotes an image display panel; 122, a scanningcircuit; 123, a control circuit; and 124, a shift register. Referencenumeral 125 denotes a line memory; 126, a synchronizing signalseparation circuit; and 127, a modulation signal generator; andreference symbols Vx and Va denote DC voltage sources.

The display panel 121 is connected to an outside electric circuit viathe terminals Dox1 to Doxm, the terminals Doy1 to Doyn, and the highvoltage terminal Hv. A scanning signal for sequentially driving theelectron source provided in the display panel, that is, the group ofelectron-emitting devices wired in a matrix shape of M rows and Ncolumns by one row (N devices) is applied to the terminals Dox1 to Doxm.

A modulation signal for controlling an output electron beam of eachdevice of the electron-emitting devices of one row selected by thescanning signal is applied to the terminals Doy1 to Doyn. A DC voltageof, for example, 10 k[V] is supplied to the high voltage terminal Hvfrom the DC voltage source Va. This is an acceleration voltage forgiving sufficient energy for exciting phosphors to an electron beamemitted from the electron-emitting device.

The scanning circuit 122 will be described. This circuit is providedwith M switching elements in its inside (in the figure, the switchingelements are schematically shown as S1 to Sm). The respective switchingelements select one of an output voltage of the DC voltage source Vx and0[V] (ground level) and are electrically connected to the terminals Dox1to Doxm of the display panel 121. The respective switching elements ofS1 to Sm operate based upon a control signal Tscan outputted by thecontrol circuit 123 and can be constituted by combining a switchingelement such as an FET.

In the case of this example, the DC voltage source Vx is set so as tooutput a constant voltage for bringing a drive voltage to be applied toa device, which has not been scanned, to be equal to or lower than anelectron emission threshold voltage based upon the characteristic(electron emission threshold voltage) of the electron-emitting device.

The control circuit 123 has a function of matching operations ofrespective parts such that appropriate display is performed based uponan image signal inputted from the outside. Based on a synchronizingsignal Tsync sent from the synchronizing signal separation circuit 126,the control circuit 123 generates control signals of Tscan, Tsft, andTmry for the respective parts.

The synchronizing signal separation circuit 126 is a circuit forseparating a synchronizing signal component and a luminance signalcomponent from a television signal of the NTSC system inputted from theoutside and can be constituted by using a general frequency separation(filter) circuit or the like. Although the synchronizing signalseparated by the synchronizing signal separation circuit 126 consists ofa vertical synchronizing signal and a horizontal synchronizing signal,it is illustrated as the Tsync signal for convenience's sake ofexplanation here. The luminance signal component of the image separatedfrom the television signal is represented as a DATA signal forconvenience's sake. The DATA signal is inputted to the shift register124.

The shift register 124 serial/parallel converts the DATA signal, whichis inputted serially in time series, for every line of an image andoperates based upon the control signal Tsft sent from the controlcircuit 123 (i.e., it can be said that the control signal Tsft is ashift clock of the shift register 124). Serial/parallel converted datafor one line of an image (equivalent to drive data for N devices of theelectron-emitting device) is outputted from the shift register 124 as Nparallel signals of Id1 to Idn.

The line memory 125 is a storage device for storing the data for oneline of an image only for a necessary time and stores contents of Id1 toIdn appropriately in accordance with the control signal Tmry sent fromthe control circuit 123. The stored contents are outputted as I′d1 toI′dn and inputted in the modulation signal generator 127.

The modulation signal generator 127 is a signal source for driving tomodulate the respective electron-emitting devices appropriatelyaccording to the respective image data I′d1 to I′dn, and an outputsignal thereof is applied to the electron-emitting devices in thedisplay panel 121 through the terminals Doy1 to Doyn.

The electron-emitting device of the present invention has the followingbasic characteristics with respect to an emission current Ie. That is,electron emission has a clear threshold voltage Vth, and the electronemission occurs only when a voltage equal to or higher than Vth isapplied to the electron-emitting device. In response to the voltageequal to or higher than the electron emission threshold, an emissioncurrent changes according to a change in an applied voltage to thedevice. Consequently, in the case in which a voltage is applied to thedevice, for example, although the electron emission does not occur evenif a voltage equal to or lower than the electron emission threshold isapplied to the device, an electron beam is outputted in the case inwhich a voltage equal to or higher than the electron emission thresholdis applied thereto. In that case, it is possible to control theintensity of the outputted electron beam by changing an applied voltageVf. In addition, in the case in which a pulse voltage is applied to thisdevice, it is possible to control the intensity of the electron beam bychanging a height Ph of a pulse and control a total amount of charges ofthe outputted electron beam by changing a width Pw of the pulse.

Therefore, a voltage modulation system, a pulse width modulation system,or the like can be adopted as a system for modulating theelectron-emitting device according to an input signal. In implementingthe voltage modulation system, a circuit of the voltage modulationsystem, which generates a voltage pulse of a fixed length to modulate apeak value of the pulse appropriately according to data to be inputted,can be employed as the modulation signal generator 127.

In implementing the pulse width modulation system, a circuit of thepulse width modulation circuit, which generates a voltage pulse of afixed peak value to modulate a width of the voltage pulse appropriatelyaccording to data to be inputted, can be employed as the modulationsignal generator 127.

As the shift register 124 and the line memory 125, those of both adigital signal system and an analog signal system can be adopted. Thisis because serial/parallel conversion and storage of an image signalonly have to be performed at a predetermined speed.

In the case in which the digital signal system is used, it is necessaryto change the output signal DATA of the synchronizing signal separationcircuit 126 into a digital signal. For this purpose, an A/D converteronly has to be provided in an output section of the synchronizing signalseparation circuit 126. In relation to this, a circuit used in themodulation signal generator 127 is slightly different depending uponwhether the output signal of the line memory 125 is a digital signal oran analog signal. That is, in the case of the voltage modulation systemusing a digital signal, for example, an D/A conversion circuit is usedfor the modulation signal generator 127 and, if necessary, anamplification circuit or the like is added thereto. In the case of thepulse width modulation system, for example, a circuit, in which ahigh-speed oscillator, a counter for counting a wave number to beoutputted by the high-speed oscillator, and a comparator for comparingan output value of the counter and an output value of the memory arecombined, is used as the modulation signal generator 127. If necessary,an amplifier for modulating a modulation signal subjected to pulse widthmodulation to be outputted by the comparator to a drive voltage of theelectron-emitting device can also be added.

In the case of the voltage modulation system using an analog signal, forexample, an amplification circuit using an operational amplifier or thelike can be adopted as the modulation signal generator 127 and, ifnecessary, a level shift circuit or the like can be added thereto. Inthe case of the pulse width modulation system, for example, a voltagecontrol oscillation circuit (VCO) can be adopted and, if necessary, anamplifier for amplifying a modulation signal to a drive voltage of theelectron-emitting device can be added thereto.

In the image display apparatus to which the present invention isapplicable, which can take the structure as described above, a voltageis applied to the respective electron-emitting devices via the terminalsoutside the case Dox1 to Doxm and Doy1 to Doyn, whereby electronemission occurs. A high voltage is applied to the metal back 105 or atransparent electrode (not shown) via the high voltage terminal Hv toaccelerate an electron beam. Accelerated electrons collide against afluorescent film and light emission occurs, whereby an image is formed.

The structure of the image display apparatus described here is anexample of the image display apparatus to which the present invention isapplicable, and various modifications are possible based upon thetechnical idea of the present invention. As to an input signal, the NTSCsystem is described as an example. However, the input signal is notlimited to this and, other than a PAL system and an SECAN system, a TVsignal (e.g., high definition TV typified by an MUSE system or the like)system consisting of more scanning lines than those of the PAL and SECAMsystems can be adopted.

The image display apparatus of the present invention can also be used asan image display apparatus or the like as an optical printer constitutedby using a photosensitive drum or the like other than as a displayapparatus for television broadcast and a display apparatus for atelevision conference system, a computer, or the like.

EMBODIMENTS

Embodiments of the present invention will be hereinafter described indetail.

First Embodiment

A manufacturing process of an electron-emitting device manufacturedaccording to this embodiment will be described in detail using FIGS.8A(a) to 8A(c).

First, quartz was used as a substrate 1 and, after sufficiently cleaningthe substrate, a film of Ta with a thickness of 500 nm was formed as acathode electrode 5 by the sputtering method (FIG. 8A(a)).

Subsequently, a carbon film 2 with a nickel concentration of 0.02% wasdeposited to have a thickness of about 12 nm on the cathode electrode 5by the sputtering method (FIG. 8A(b)). Ar was used as an atmosphericgas. Conditions are as described below.

-   rf power supply: 13.56 MHz-   rf power: 400 W-   Gas pressure: 267 mPa-   Substrate temperature: 300° C.-   Target: Mixed target of graphite and nickel

Next, the substrate was subjected to heat treatment by lamp heating at600° C. for 300 minutes in hydrogen containing atmosphere. Then, asshown in FIG. 8A(c), nickel cohered and a plurality of particles 3 whichmainly includes nickel were formed. As shown in FIG. 8A(c), aggregates(groups of particles) 10 of metal particles 3 exist a film thickness ofthe carbon film 2 or more apart from each other. A concentration P ofnickel particles 3 formed by the heat treatment was P=1×10¹⁶/cm³according to TEM observation.

An electron-emitting characteristic of the electron-emitting devicecomprising the layer 2 and the cathode electorde 5 manufactured in thisembodiment was measured. With the electron-emitting device manufacturedin this embodiment as a cathode, a voltage was applied to an anode (withan area of 1 mm²), which is parallel with the layer (electron-emittingfilm) 2, 1 mm apart from the layer 2. A voltage/current characteristicof the electron-emitting device is shown in FIG. 9. Note that thehorizontal axis indicates an electric field intensity and the verticalaxis indicates an emission current density.

In the electron-emitting device manufactured in this embodiment, therewas no remarkable electrical breakdown, that is, a satisfactoryelectron-emitting characteristic without conditioning could be observed.

Second Embodiment

A manufacturing process of an electron-emitting device manufacturedaccording to this embodiment will be described in detail using FIGS.8B(a) to 8B(c).

First, quartz was used as a substrate 1 and, after sufficiently cleaningthe substrate, a film of Ta with a thickness of 500 nm was formed as acathode electrode 5 by the sputtering method (FIG. 8B(a)).

Subsequently, a carbon film 2 with a cobalt concentration of 0.3% and ahydrogen concentration of 1% was deposited to have a thickness of about12 nm on the cathode electrode 5 by the sputtering method (FIG. 8B(b)).A mixed gas of Ar and H₂ with a mixture ratio of 1:1 was used as anatmospheric gas. Conditions are as described below.

-   rf power supply: 13.56 MHz-   graphite rf power: 1 KW-   cobalt rf power: 10 W-   Gas pressure: 267 mPa-   Substrate temperature: 300° C.-   Target: Mixed target of graphite and cobalt

Next, the substrate was subjected to heat treatment by lamp heating at600° C. for 60 minutes in a mixed gas atmosphere of acetylene andhydrogen. Reaction was faster than that at the time of the hydrogenatmosphere described in the first embodiment, and cobalt cohered andcobalt particles 3 of a crystal structure were formed (FIG. 8B(c)). Atthis point, in parts other than the cohered cobalt particles 3, cobaltwas equal to or less than a detection limit in EDAX measurement. Aconcentration of cobalt particles formed by the heat treatment wasp=1×10¹⁷/cm³ according to the TEM observation.

An electron-emitting characteristic of the electro-emitting devicemanufactured in this embodiment can be measured as well as embodiment 1.With the electron-emitting device manufactured in this embodiment as acathode, a voltage was applied to an anode, which is parallel with theelectron-emitting film, 1 mm apart from the electron-emitting device. Asa result, there was no remarkable electrical breakdown, that is, asatisfactory electron-emitting characteristic without conditioning couldbe observed. Moreover, an electron-emitting film with smaller hardnessand less stress compared with the first embodiment could be formed.

Third Embodiment

A manufacturing process of an electron-emitting device manufacturedaccording to this embodiment will be described in detail using FIGS. 10Ato 10C.

First, as shown in FIG. 10A, an n⁺Si substrate was used as a substrate 1and a film of Ta with a thickness of 500 nm was formed as a cathodeelectrode 5. Subsequently, a carbon film 2 was deposited to have athickness of about 30 nm by the HFCVD method. An apparatus diagram ofthe HFCVD method is shown in FIG. 11.

In FIG. 11, reference numeral 21 denotes a vacuum container; 22, asubstrate; 23, a substrate holder; 24, a heat source for dissolvingthermoelectron and material gas to generate ions; 25, a substrate biaselectrode for applying a voltage to the substrate; 26, an electrode forextracting thermoelectron from the heat source 24; 27, a monitoringmechanism for observing a substrate voltage and a current flowing to thesubstrate; 28, a power supply for applying a voltage to the substrate;29, a current monitoring mechanism for monitoring a substrate current;30, a voltage application mechanism for applying a voltage to athermoelectron extraction electrode; 31, a power supply for applying avoltage to the thermoelectron extracting electrode; 32, a film formationprocess control mechanism for controlling the mechanisms 27 and 30; 33,a gas introducing port; and 34, an exhaust pump for exhaust the vacuumcontainer 21.

Note that the substrate holder 23 and the substrate bias electrode 25may be insulated by a ceramic plate or the like. In addition, a voltageis inputted to the heat source 24 by a not-shown power supply, and theheat source 24 is heated to a desired temperature. The power supply atthis point may be direct current or alternating current. Moreover, thefilm formation process control mechanism 32 may be controlled by apersonal computer or the like or may have a structure which can becontrolled manually.

In an HFCVD apparatus shown in FIG. 11, an n⁺Si substrate was arrangedon the substrate bias electrode 25 and the vacuum container 21 wasexhausted to 1×10⁻⁵ Pa using the exhaust pump 34. Next, hydrogen gas of10 sccm was introduced from the gas introducing port 33 and the vacuumcontainer 21 was held at 1×10⁻¹ Pa. Thereafter, after applying an ACvoltage of 14 V to the heat source 24 to heat it to 2100° C., a DCvoltage of 150 V was applied to the substrate bias electrode 25 usingthe voltage application mechanism 27, and a current value of 0.5 mA wasobserved by the current monitor 29. This state was held for 20 minutesand substrate cleaning was performed.

Next, the introduction of hydrogen gas was stopped and, after exhaustingthe vacuum container 21 to 1×10⁻⁵ Pa again, the vacuum container 21 washeld at 1×10⁻¹ Pa. Next, after setting the substrate 22 to 30° C. usinga substrate heating mechanism, a DC voltage of −150 V was applied to thesubstrate bias electrode 25. Next, an AC voltage of 15 V was applied tothe heat source 24 to heat it to 2100° C. Next, a voltage was applied tothe thermoelectron extracting electrode 26 and ions were irradiated onthe substrate 22. At this point, a voltage value of the thermoelectronextracting electrode 26 was set to 90 V such that a current amountobserved by the current monitoring mechanism 29 becomes 5 mA, and thesubstrate 22 was held in this state for 10 minutes to form a DLC film 2with many SP³ bondings.

Subsequently, cobalt was injected into the DLC (diamond-like-carbon)film by the ion implantation method at 25 keV and with a dose amount of3×10¹⁶/cm² (FIG. 10B).

Next, the substrate was subjected to heat treatment by lamp heating at550° C. for 300 minutes in an acetylene 0.1% atmosphere (99.9%hydrogen). Then, as shown in FIG. 10C, cobalt cohered and cobaltparticles 3 of a crystal structure were partially formed on a surfacelayer (layer 2). In addition, aggregates (groups of particles) 10 of thecobalt particles 3 were formed discretely in the layer 2. At this point,in the carbon film in parts other than the cohered cobalt particles,cobalt was equal to or less than a detection limit in EDAX measurement.On the other hand, in parts (layer 2′) close to an interface between theDLC film and the Si substrate, a density of the cobalt particles washigh and most of them function as a conductor(conductive layer). In asectional TEM image, it was seen that the cobalt particles 3 existed ina monocrystal state in the DLC film 2. When the image was furtherenlarged, it was observed that a graphite layer grew around the Coparticles. A concentration of the cobalt particles formed by the heattreatment was P=5×10¹⁶/cm³ according to the TEM observation. A hydrogenconcentration was 4%.

In addition, when unevenness of the surface of the layer 2 was evaluatedwith an AFM, it was found that planarity was secured at values of 4.4 nmas a P-V (peak to valley) value (maximum value—minimum value) and 0.28nm as rms.

An electron-emitting characteristic of the electron-emitting device thusmanufactured was measured. With the electron-emitting devicemanufactured in this embodiment as a cathode, a voltage was applied toan anode (with an area of 1 mm²), which is parallel with theelectron-emitting device, 1 mm apart from the electron-emitting device.A volt-ampere characteristic at this point is shown in FIG. 12. Notethat the horizontal axis indicates an electric field intensity and thevertical axis indicates an emission current density.

In the electron-emitting device manufactured in this embodiment, therewas no remarkable breakdown, that is, a satisfactory electron-emittingcharacteristic without conditioning could be observed. An electronemission site density (ESD) was 1×10⁶/cm² or more, and an emissioncurrent density was as large as 10 mA/cm² or more.

Fourth Embodiment

A manufacturing process of an electron-emitting device manufacturedaccording to this embodiment will be described in detail using FIGS. 13Ato 13C.

An n⁺Si substrate was used as a substrate 1 and a film of Ta with athickness of 500 nm was formed as a cathode electrode 5 by thesputtering method. Subsequently, a DLC film 2 was deposited to have athickness of about 15 nm by the HFCVD method (similarly to the thirdembodiment). A film thickness was adjusted by shortening time.

Subsequently, the DLC film 2 was subjected to resist application andpatterning and, thereafter, cobalt was injected by the ion implantationmethod in the DLC film 2 at 25 keV and with a dose amount of 5×10¹⁶/cm²(FIG. 13B). Cobalt was partially injected only in areas where resist Rwas not arranged. RP was in the silicon substrate, and only a lowconcentration layer of cobalt of the third embodiment was formed in acarbon film. Since the DLC film was subjected to patterning and ionimplantation, places where particles containing metal are formed aredetermined, and areas arranged from a cathode electrode side to thesurface of the DLC film 2 (aggregates 10 of particles) are never formedadjacent to each other in the DLC film 2 but are discretely arranged ina plural form even if an ion implantation concentration is high.

Next, the substrate was subjected to heat treatment by lamp heating at750° C. for 60 minutes in an acetylene 0.1% atmosphere (99.9% hydrogen).Then, as shown in FIG. 13C, cobalt cohered and cobalt particles 3 of acrystal structure were formed in high concentration. When the image wasfurther enlarged, it was observed that a microstructure of graphite(graphens) 4 was formed around Co particles.

An electron-emitting characteristic of the electro-emitting device thusmanufactured was measured. With the electron-emitting devicemanufactured in this embodiment as a cathode, a voltage was applied toan anode, which is parallel with the electron-emitting device, 1 mmapart from the electron-emitting device. As a result, there was noremarkable breakdown, that is, a satisfactory electron-emittingcharacteristic without conditioning could be observed.

Fifth Embodiment

A manufacturing process of an electron-emitting device manufacturedaccording to this embodiment will be described in detail using FIGS.14A, 14B, and 14C.

An n⁺Si substrate was used as a substrate 1 and a film of Ta with athickness of 500 nm was formed as a cathode electrode 5 by thesputtering method. Subsequently, a DLC film 2 was deposited to have athickness of about 15 nm by the HFCVD method similarly to the thirdembodiment (FIG. 14A).

Subsequently, a silicon oxide film 200 was formed to have a thickness of25 nm by the sputtering method. Thereafter, cobalt was injected in thesilicon oxide film and the DLC film by the ion implantation method at 25keV and with a dose amount of 5×10¹⁵/cm² (FIG. 14B). RP is in thesilicon oxide film and concentration is as high as 1% on the surface ofthe DLC.

After removing the silicon oxide film with buffered hydrofluoric acid,the substrate was subjected to heat treatment by lamp heating at 550° C.for 300 minutes in an acetylene 0.1% atmosphere (99.9% hydrogen). Then,as shown in FIG. 14C, cobalt cohered and cobalt particles 3 of a crystalstructure were formed in high concentration with 2×10¹⁷/cm³ on thesurface thereof.

An electron-emitting characteristic of the electro-emitting device thusmanufactured was measured. With the film manufactured in this embodimentas a cathode, a voltage was applied to an anode, which is parallel withthe electron-emitting film, 1 mm apart from the electron-emittingdevice. As a result, there was no remarkable breakdown, that is, asatisfactory electron-emitting characteristic without conditioning couldbe observed. Although a threshold value for electron emission was highbut there were many emission sites compared with the third embodiment,and an ESD was 1×10⁷/cm² or more and a current density of 10 mA/cm² ormore was obtained.

Sixth Embodiment

A manufacturing process of an electron-emitting device manufacturedaccording to this embodiment will be described in detail using FIG. 15.

First, quartz was used as a substrate 1 and, after sufficiently cleaningthe substrate 1, a film of Ta with a thickness of 500 nm was formed as acathode electrode 5 by the sputtering method.

Subsequently, a carbon film 6 was deposited to have a thickness of about12 nm on the cathode electrode 5 by the sputtering method. Ar/H₂ wasused as an atmospheric gas. Conditions are as described below.

-   rf power supply: 13.56 MHz-   rf power: 400 W-   Gas pressure: 267 mPa-   Substrate temperature: 300° C.-   Target: Graphite

Subsequently, a carbon film of cobalt concentration of 8% was depositedto have a thickness of about 12 nm on the carbon film 6 with amulti-target of cobalt and graphite as a target. As an atmospheric gas,Ar/H₂ was used. Conditions are as shown below.

-   rf power supply: 13.56 MHz-   Graphite rf power: 600 W-   Cobalt rf power: 10 W-   Gas pressure: 267 mP·BR>Substrate temperature: 300° C.-   Target: Graphite and cobalt    Note that, in this process, a power on the graphite target side was    increased and a cobalt ratio was gradually reduced. On the surface    of the substrate, a Co concentration was set to 0.1%.

Next, the substrate was subjected to heat treatment at 600° C. for 300minutes in an acetylene 0.1% atmosphere (99.9% hydrogen). Then, as shownin FIG. 15, cobalt cohered and cobalt particles 3 of a crystal structurewere formed. A laminated structure was formed in which a Ta electrode 5,a high resistance layer 6 composed of amorphous carbon, a lowresistance. Co—C layer 2′ with Co particles 3 arranged in a highconcentration, and a layer 2 with Co particles 3 arranged in a lowconcentration were laminated in this order. In the layer 2, areas(aggregates of particles) 10 in which the cobalt particles 3 werearranged from the cathode electrode 5 side toward the surface of thelayer 2 were discretely formed. In such a structure, the high resistancelayer 6 of the bottom layer functions as a current restrictionresistance preventing electrons from being emitted excessively at thetime of electron emission and contributes to uniform electron emission.In the low resistance layer 2′ in the middle, a density of cobaltparticles is high, and electrons passed through the high resistancelayer 6 enters the cobalt particles and conducts upward with an electricfield. This low resistance layer 2′ acts as a conductor rather than adielectric body. In the vicinity of the surface of the substrate, adensity of cobalt particles is low, there is obtained a structure inwhich electric field concentration is likely to occur, and electrons areemitted into vacuum.

An electron-emitting characteristic of the electro-emitting device thusmanufactured was measured. With the electron-emitting devicemanufactured in this embodiment as a cathode, a voltage was applied toan anode, which is parallel with the electron-emitting device, 1 mmapart from the electron-emitting device. As a result, there was noremarkable breakdown, that is, a satisfactory electron-emittingcharacteristic without conditioning and which shows a uniform lightemitting characteristic could be observed.

Seventh Embodiment

A schematic sectional view of an electron-emitting device manufacturedaccording to this embodiment is shown in FIG. 16A, and a schematic planview thereof is shown in FIG. 16B.

Reference numeral 1 denotes a substrate; 5, a cathode electrode; 7, aninsulating layer; 8, a gate electrode; and 2, an electron-emitting film.In addition, reference symbol W1 denotes a diameter of a hole providedin the gate electrode 8. Reference symbol Vg denotes a voltage appliedbetween the gate electrode 8 and the cathode electrode 5; Va, a voltageapplied between the gate electrode 8 and the anode 12; and Ie, anelectron emission current.

When Vg and Va are applied in order to drive the device, a strongelectric field is formed in the hole, and a shape of an equipotentialsurface inside the hole is determined according to Vg, a thickness and ashape of the insulating layer 7, or a dielectric constant or the like ofthe insulting layer. Outside the hole, a substantially parallelequipotential surface is obtained due to Va, although mainly dependingupon a distance H between the cathode electrode 5 and the anode 12.

When an electric field applied to the electron-emitting film 2 exceeds acertain threshold value, electrons are emitted from theelectron-emitting film. Electrons emitted from the hole are acceleratedtoward the anode 12 this time and collide against phosphors (not shown)provided in the anode 12 to emit light.

A manufacturing process of the electron-emitting device of thisembodiment will be hereinafter described in detail using FIGS. 4A to 4D.

(Step 1)

First, as shown in FIG. 4A, quartz was used as the substrate 1 and,after sufficiently cleaning the substrate 1, a film of Ta with athickness of 500 nm was formed as the cathode electrode 5 by thesputtering method.

(Step 2)

Subsequently, the carbon film 2 was deposited to have a thickness of 30nm by the HFCVD method. At this point, the carbon film 2 was formed withconditions under which DLC grows. Growing conditions are shown below.

-   Gas: CH₄-   Substrate bias: −50 V-   Gas pressure: 267 mPa-   Substrate temperature: Room temperature-   Filament: Tungsten-   Filament temperature: 2100° C.-   Back bias: 100 V    (Step 3)

Subsequently, cobalt was injected into the DLC film 2 by the ionimplantation method at 25 keV and with a dose amount of 3×10¹⁶/cm².

(Step 4)

Next, the substrate was subjected to heat treatment by lamp heating at550° C. for 60 minutes in an acetylene 0.1% atmosphere (99.9% hydrogen).

(Step 5)

Next, as shown in FIG. 4B, SiO₂ with a thickness of 1 μm and Ta with athickness of 100 nm were deposited as the insulating layer 7 and thegate electrode 8, respectively, in this order.

(Step 6)

Next, as shown in FIG. 4C, spin coating and a photo mask pattern of apositive photoresist (AZ1500/manufactured by Clariant Corporation) wasexposed and developed by photolithography to form a mask pattern.

(Step 7)

As shown in FIG. 4D, the gate electrode 8 of Ta was dry-etched using CF₄gas with the mask pattern as a mask and, subsequently, the SiO₂ film 7was etched by buffered hydrofluoric acid to form the opening 9.

(Step 8)

The mask pattern was completely removed to complete theelectron-emitting device of this embodiment. Note that a film stress waslittle and film peeling or other problems in process did not occur.

As shown in FIGS. 16A and 16B, the anode electrode 12 was arranged abovethe electron-emitting device manufactured as described above, and avoltage is applied between the electrodes 5 and 8 to drive the device.FIG. 17 is a graph of a volt-ampere characteristic of theelectron-emitting device manufactured by the above-mentioned formation.According to the present invention, electrons could be emitted with alow voltage. An electron source could be formed with actual voltagesVg=20 V and Va=10 kV and the distance H between the electron-emittingdevice and the anode 12 set to 1 mm.

Here, although an electron-emitting part is described as a substantiallycircular hole as shown in FIGS. 16A and 16B, a shape of thiselectron-emitting part is not specifically limited and it may be formedin, for example, a line shape. A manufacturing method is completely thesame except that only a patterning shape is changed. It is also possibleto arrange a plurality of line patterns and it becomes possible tosecure a large emission area.

Eighth Embodiment

A manufacturing process of an electron-emitting device manufacturedaccording to this embodiment will be described in detail using FIGS. 19Ato 19C.

First, quartz was used as a substrate 1 and, after sufficiently cleaningthe substrate 1, a film of Ta with a thickness of 500 nm was formed as acathode electrode 5 by the sputtering method. Subsequently, a carbonlayer 211 containing 0.8% cobalt was deposited on the cathode electrode5 using a carbon target containing cobalt with a cobalt concentration of1.0% and a target of graphite by the sputtering method (FIG. 19A).

Subsequently, a carbon layer 212 not containing cobalt was deposited tohave a thickness of several tens nm on the carbon layer 211 by usingonly a graphite target (FIG. 19B).

Next, the substrate was subjected to heat treatment by lamp heating at600° C. for 60 minutes in a mixed gas atmosphere of acetylene andhydrogen to form particulates 213 containing Co as a main body in thelayer 211 so as to overlap in a film thickness direction (FIG. 19C).

As in this embodiment, the carbon layer 211 containing cobalt is coatedby the carbon layer 212 not containing cobalt, whereby a carbon filmcontaining cobalt of a higher concentration can be manufactured whilesuppressing growth of a foreign body on the surface of the layer 211. Aconcentration of cobalt particles in the layers (areas denoted by 211and 212) formed in this embodiment was P=3×10¹⁷/cm³ according to the TEMobservation. In addition, after arranging the anode electrode so as tobe opposed to the electron-emitting device (the cathode electrode 5 andthe carbon films (211 and 212)) manufactured in this embodiment, when avoltage was applied between the cathode electrode and the anodeelectrode to measure an electron-emitting characteristic, anelectron-emitting site density could be improved.

Ninth Embodiment

Carbon films (211, 212) were formed using the same film formationapparatus as that in the eighth embodiment. However, in this embodiment,the rf power of the carbon target containing cobalt was changed from 100W to 700 W as time elapsed and an area of a low cobalt concentration wasformed in the vicinity of an interface of a substrate 1 to form a highresistance film. As a result, fluctuation at the time of electronemission could be reduced and a stable electron-emitting characteristicwas obtained.

Tenth Embodiment

Carbon films (211, 212) were formed on a cathode electrode 5 under thesame conditions as those in the eighth embodiment, and a substrate wassubjected to heat treatment by lamp heating in a mixed gas atmosphere ofacetylene and hydrogen. However, in this embodiment, a carbon layer notcontaining cobalt was removed by hydrogen plasma after the heattreatment to expose a part of cobalt particles such that electrons wereemitted to the vacuum more easily (see FIG. 20). As a result, anelectron-emitting film capable of emitting electrons with a lowerelectric field could be formed.

Eleventh Embodiment

Schematic views of an electron-emitting device manufactured according tothis embodiment are shown in FIGS. 21 and 22. FIG. 21 is a schematicsectional view and FIG. 22 is a schematic plan view.

Reference numeral 1 denotes a substrate; 2, an electron-emitting film;5, a cathode electrode; 7, an insulating layer; 8, a gate electrode; and210, a focusing electrode. By providing the focusing electrode 201, anelectron beam of higher precision can be obtained.

A manufacturing method of the electron-emitting device manufactured inthis embodiment will be described using FIGS. 23A to 23D.

First, a Ta electrode is deposited to have a thickness of 500 nm on thequartz substrate 1 by the sputtering method to form the cathodeelectrode 5. Subsequently, a diamond-like-carbon film (DLC film) 2 wasformed to have a thickness of 25 nm by the heat filament CVD method(HFCVD method), and then, Al was deposited to have a thickness of 25 nmby the sputtering method to form the focusing electrode 201.Subsequently, the silicon oxide film 7 was deposited to have a thicknessof 500 nm and Ta was deposited to have a thickness of 100 nm as the gateelectrode 8 to form a laminated structure shown in FIG. 23A.

Next, opening areas of φ1 μm were formed in the Ta film 8 and thesilicon oxide film 7 by the photolithography (FIG. 23B). Morespecifically, the formation of the opening areas was stopped at thepoint when the substrate was removed up to the silicon oxide film byetching.

Next, cobalt ions were injected into the laminated structure by the ionimplantation method at 25 keV with a dose amount of 5×10¹⁵/cm² (FIG.23C). In this embodiment, since Co ions were injected into the carbonfilm 2 in a state in which the Al layer 201 was arranged, a Coconcentration can be set simply so as to be the highest in the vicinityof the surface of the carbon film 2.

Subsequently, after etching to remove the Al layer 201 with phosphoricacid, the carbon film 2 was subjected to heat treatment by lamp heatingin a mixed gas atmosphere of acetylene and hydrogen (FIG. 23D).

When the electron-emitting device thus manufactured was arranged in avacuum container, and a voltage of 3 kV was applied to an anodeelectrode (having phosphors on its surface) arranged in a position 1 mmapart from the cathode electrode 5 and, at the same time, a potentialfor extracting electrons from the carbon film 2 was applied to the gateelectrode 8, whereby electrons were emitted toward the anode electrodefrom the carbon film 2 to drive the device, an emitted light image wasobserved in the phosphors. When this result was compared with theemitted light image of electron beams emitted from the electron-emittingdevice manufactured in the seventh embodiment, a beam size (emittedlight image) was reduced and high precision was achieved. According tothis embodiment, by using the focusing electrode 201 together with anion implantation mask, high precision and simplification of amanufacturing process was achieved and low cost was realized.

Twelfth Embodiment

In this embodiment, the surface of the carbon film 2 in the secondembodiment was actively terminated with hydrogen. More specifically, theheat treatment in the mixed gas atmosphere of acetylene and hydrogen inthe second embodiment was replaced by heat treatment at 60 degrees for60 minutes in an atmosphere of a total pressure of 7 Kpa (70% methaneand 30% hydrogen). The other parts of manufacturing process are the sameas those of the second embodiment.

When a characteristic of electron emission from the carbon filmmanufactured according to this embodiment was measured in the samemanner as that of the second embodiment, a voltage at which electronemission was started was halved and, at the same time, an electronemission amount itself, which was obtained when the same potential asthe potential applied to the carbon film 2 of the second embodiment wasapplied, also increased and an ESD also increased by two digits.

Note that, although the heat treatment in the mixed atmosphere ofhydrocarbon and hydrogen under the above-mentioned conditions wasdescribed in this embodiment as the hydrogen termination treatment onthe surface of the carbon film (layer) 2, hydrogen termination treatmentis not limited to the above-mentioned example. The hydrogen terminationtreatment may be performed according to other method.

Thirteenth Embodiment

The image display apparatus was manufactured using the electron-emittingdevice manufactured in the above-mentioned seventh embodiment. Thedevices described in the seventh embodiment were arranged in a matrixshape of 100×100. The wirings on the X side were connected to thecathode electrode 5 and the wirings on the Y side were connected to thegate electrode 8 as shown in FIG. 5. The devices were arranged at apitch of 300 μm horizontally and 300 μm vertically. Phosphors werearranged above the devices. As a result, an image display apparatus,which could be driven in matrix and is high in luminance and precision,could be formed.

Fourteenth Embodiment

Schematic views of an electron-emitting device manufactured according tothis embodiment are shown in FIGS. 24A to 24D and 25. FIGS. 24A to 24Dare schematic sectional views of a manufacturing process of theelectron-emitting device manufactured in this embodiment. FIG. 25 is aschematic plan view of the electron-emitting device obtained in FIGS.24A to 24D.

A manufacturing method for the electron-emitting device manufactured inthis embodiment will be described using FIGS. 24A to 24D.

First, a conductive film 241 composed of Ta was deposited to have athickness of 100 nm using the sputtering method on an insulatingsubstrate 1. Subsequently, after a carbon film 2 was formed to have athickness of 35 nm on the conductive film composed of Ta by the heatfilament CVD method (HFCVD method), an insulating layer composed of asilicon oxide film 242 was deposited to have a thickness of 30 nm on thecarbon film.

Next, a gap 243 with a width W of 2 μm was formed in the silicon oxidefilm, the carbon film, and the conductive film by the photolithography(FIG. 24B).

Next, after removing a resist, cobalt ions were implanted into alaminated body of the carbon film and the silicon oxide film layer at 25keV and with a dose amount of 1×10¹⁵/cm² (FIG. 24C) by ion implantationmethod. In this embodiment, since the Co ions were implanted into thecarbon film in a state in which the silicon oxide film layer wasarranged, a Co concentration could be easily set so as to be the highestin the vicinity of the surface of the carbon film.

Subsequently, after etching to remove the silicon oxide film layer, thecarbon film 2 was subjected to heat treatment by lamp heating in a mixedgas atmosphere of acetylene and hydrogen (FIG. 24D). According to thisprocess, there was formed the layer 2 in which a plurality of Coparticles were arranged in a film thickness direction.

When electrons were emitted to be driven from the layer 2 by setting theelectron-emitting device thus-manufactured in a vacuum container,applying a voltage of 5 kV to an anode electrode (having phosphors onits surface) arranged in a position 1 mm apart upward from the substrate1 and, at the same time, applying a drive voltage to the cathodeelectrode 5 and the gate electrode 8, an emitted light image from thephosphors could be observed with a low drive voltage.

Note that, although a form in which the layer 2 remains on the gateelectrode 8 is described in this embodiment, it is not always necessarythat the layer 2 remains on the gate electrode 8.

Effects of the Invention

As described above, the present invention can provide anelectron-emitting device which does not include a process ofconditioning and is capable of emitting electrons with a low thresholdvalue. Moreover, the present invention can provide an electron-emittingdevice with which the spot size of an electron beam is small, highlyefficient electron emission is possible with a low voltage, and amanufacturing process is easy.

In addition, when the electron-emitting device of the present inventionis applied to an electron source and an image display apparatus, anelectron source and an image display apparatus excellent in performancecan be realized.

1. An electron-emitting device comprising: a cathode electrode; a layerelectrically connected to the cathode electrode; and a plurality ofparticles, each comprising as a main component a material which hasresistivity lower than resistivity of a material of the layer, whereinthe plurality of particles are arranged in the layer; and a density ofthe particles in the layer is 1×10¹⁴/cm³ or more and 5×10¹⁸/cm³ or less.2. An electron-emitting device comprising: a cathode electrode; a layerelectrically connected to the cathode electrode; and a plurality ofparticles, each comprising as a main component a material, which hasresistivity lower than resistivity of a material of the layer, wherein,the plurality of particles are arranged in the layer; and aconcentration of a main element of the particles with respect to a mainelement of the layer is 0.001 atm % or more and 1.5 atm % or less.
 3. Anelectron-emitting device comprising: a cathode electrode; a layerelectrically connected to the cathode electrode; and a plurality ofparticles, each comprising as a main component a material which hasresistivity lower than resistivity of a material of the layer, whereinthe plurality of particles are arranged in the layer; a density of theparticles in the layer is 1×10¹⁴/cm³ or more and 5×10¹⁸/cm³ or less; anda concentration of a main element of the particles with respect to amain element of the layer is 0.001 atm % or more and 1.5 atm % or less.4. An electron-emitting device comprising: a cathode electrode; a layerwhich is arranged on the cathode layer and contains carbon as a maincomponent; and at least two particles which are arranged so as to beadjacent to each other in the layer and comprises metal as a maincomponent, wherein one of the adjacent two particles is arranged to benearer to the cathode electrode than the other particle; and the metalis metal selected from Co, Ni, and Fe.
 5. An electron-emitting devicecomprising: a cathode electrode; and a layer connected to the cathodeelectrode, wherein a plurality of groups of particles, each group beingconstituted by at least two particles adjacent to each other, arearranged in the layer; each of the particles comprises as a maincomponent a material which has resistivity lower than resistivity of amaterial of the layer, the adjacent two particles are arranged in arange of 5 nm or less; one of the adjacent two particles is arranged tobe nearer to the cathode electrode than the other particle; and theplurality of groups of particles are arranged apart from each other byan average film thickness of the layer or more.
 6. An electron-emittingdevice comprising: a cathode electrode; and a layer connected to thecathode electrode, wherein a plurality of groups of particles, eachgroup being constituted by at least two particles which comprise metalas a main component and are adjacent to each other, are arranged in thelayer; the layer comprises as a main component a material which hasresistivity higher than resistivity of the particles; the adjacent twoparticles are arranged in a range of 5 nm or less; and one of theadjacent two particles is arranged to be nearer to the cathode electrodethan the other particle.
 7. An electron-emitting device comprising: acathode electrode; and a layer which is connected to the cathodeelectrode and comprises carbon as a main component, wherein a pluralityof groups of particles, each group being constituted by at least twoparticles which comprise metal as a main component and are adjacent toeach other, are arranged in the layer; the plurality of groups ofparticles are arranged apart from each other by an average filmthickness of the layer or more; and a concentration of the metal in thelayer is lower on a surface side of the layer than on the cathodeelectrode side.
 8. An electron-emitting device comprising: a cathodeelectrode; and a layer which is connected to the cathode electrode andcomprises carbon as a main component, wherein a plurality of groups ofparticles constituted by at least two particles, which comprise metal asa main component, being adjacent to each other are arranged in thelayer, one of the adjacent two particles is arranged on the cathodeelectrode than the other particle; and graphen is included betweenadjacent particles among at least part of the plurality of particles. 9.An electron-emitting device comprising: a cathode electrode; a layerwhich is electrically connected to the cathode electrode and comprisescarbon as a main component; and a plurality of conductive particlesarranged in the layer, each particle comprising carbon as a maincomponent, wherein the layer contains a hydrogen element of 0.1 atm % ormore with respect to a carbon element.
 10. An electron-emitting deviceaccording to claim 9, wherein the layer contains a hydrogen element of 1atm % or more with respect to the carbon element.
 11. Anelectron-emitting device according to claim 10, wherein the layercontains a hydrogen element of 20 atm % or less with respect to thecarbon element.
 12. An electron-emitting device according to any one ofclaims 1 to 11, wherein surface unevenness of the layer is smaller than1/10 of its film thickness in rms.
 13. An electron-emitting deviceaccording to any one of claims 1 to 3, 5, and 6, wherein the layercomprises carbon as a main component.
 14. An electron-emitting deviceaccording to any one of claims 4, 7, and 8, wherein an averageconcentration of hydrogen with respect to carbon in the layer is 0.1 atm% or more.
 15. An electron-emitting device according to any one ofclaims 4, 7, 8, and 9, wherein the layer comprising carbon as a maincomponent has an sp³ bonding.
 16. An electron-emitting device accordingto any one of claims 1 to 3, 5, and 9, wherein the particles comprisemetal as a main component.
 17. An electron-emitting device according toany one of claims 6 to 8, wherein the metal is metal selected from Co,Ni, and Fe.
 18. An electron-emitting device according to any one ofclaims 1 to 3, 5, and 9, wherein the particles comprise monocrystalmetal as a main component.
 19. An electron-emitting device according toany one of claims 1 to 9, wherein the particles have an average particlediameter of 1 nm or more to 10 nm or less.
 20. An electron-emittingdevice according to any one of claims 1 to 9, wherein the layer has athickness of 100 nm or less.
 21. An electron-emitting device accordingto any one of claims 1 to 4 and 7 to 9, wherein at least two adjacentparticles among the plurality of particles are arranged 5 nm or lessapart from each other.
 22. An electron-emitting device according to anyone of claims 4 to 9, wherein a density of the particles in the layer is1×10¹⁴/cm³ or more and 5×10¹⁸/cm³ or less.
 23. An electron-emittingdevice according to any one of claims 1 to 9, wherein a density of theparticles in the layer is 1×10¹⁵/cm³ or more and 5×10¹⁷/cm³ or less. 24.An electron-emitting device according to any one of claims 4 to 9,wherein a concentration of a main element of the particles with respectto a main element of the layer is 0.001 atm % or more and 1.5 atm % orless.
 25. An electron-emitting device according to any one of claims 1to 9, wherein a concentration of a main element of the particles withrespect to a main element of the layer is 0.05 atm % or more and 1 atm %or less.
 26. An electron-emitting device according to any one of claims1 to 3 and 9, wherein: the plurality of particles are arrangeddispersedly in the layer as a plurality of groups of particles, eachgroup being constituted by at least two adjacent particles; one of thetwo adjacent particles are placed to be nearer to the cathode electrodethan the other particle; and the plurality of groups of particles arearranged apart from each other by an average film thickness of the layeror more.
 27. An electron-emitting device according to any one of claims1 to 9, wherein the surface of the layer is terminated with hydrogen.28. An electron-emitting device according to any one of claims 1 to 9,further comprising: an insulating film which is arranged on the cathodeelectrode and has a first opening; and a gate electrode which isarranged on the insulating film and has a second opening, wherein: thefirst opening and the second opening communicate with each other; andthe layer is exposed in the first opening.
 29. An electron source,wherein a plurality of the electron-emitting devices according to anyone of claims 1 to 9 are arranged.
 30. An image display apparatus,characterized by comprising the electron source according to claim 29and a light-emitting member which emits light by being irradiated withelectrons.
 31. A manufacturing method for an electron-emitting devicecomprising: forming a layer which contains metal and comprises amaterial as a main component, the material having resistivity higherthan that of the metal, and heating the layer in an atmospherecontaining hydrogen.
 32. A manufacturing method for an electron-emittingdevice according to claim 31, wherein the atmosphere containing hydrogenfurther contains hydrocarbon.
 33. A manufacturing method for anelectron-emitting device according to claim 32, wherein the hydrocarbonis acetylene.
 34. A manufacturing method for an electron-emitting deviceaccording to any one of claims 31 to 33, wherein the metal is a VIIIgroup element.
 35. A manufacturing method for an electron-emittingdevice according to any one of claims 31 to 33, wherein the metal ismetal selected from Co, Ni, and Fe.
 36. A manufacturing method for anelectron-emitting device according to any one of claims 31 to 33,wherein a heat treatment temperature in the heating is 450° C. or more.37. A manufacturing method for an electron-emitting device according toany one of claims 31 to 33, wherein the layer comprising a materialhaving resistivity higher than that of the metal as a main component isa layer comprising carbon as a main component.
 38. A manufacturingmethod for an electron-emitting device according to claim 37, whereinthe metal is contained in the layer comprising carbon as a maincomponent before the heating at a ratio of 0.001 atm % or more and 5 atm% or less with respect to the carbon element.
 39. A manufacturing methodfor an electron-emitting device according to claim 37, wherein the metalis contained in the layer comprising carbon as a main component beforethe heating at a ratio of 0.001 atm % or more and 1.5 atm % or less withrespect to the carbon element.
 40. A manufacturing method for anelectron-emitting device according to claim 37, wherein the filmcomprising carbon as a main component before the heating has an sp³bonding.